This invention relates to pharmaceutical compositions and methods for inhibiting the proliferation of cells.
In human clinical studies with non-small cell lung cancer (NSCLC) patients, the kinase inhibitors, erlotinib and gefitinib have been found to be effective, but in only a subset of patients. It was later determined that the responsive patients had certain mutations in the gene for epidermal growth factor receptor (EGFR). The mutant forms of EGFR are enzymatically active without the need for ligand stimulation. They are also particularly sensitive to kinase inhibitors like erlotinib and gefitinib, which competitively bind to the ATP binding site of the EGFR kinase domain. Those mutations have been cataloged and described at length in the scientific literature. They include small deletions or point mutations in the kinase domain as has previously been written about extensively. See e.g., Sharma, Nat. Rev. Cancer 7:169 (2007) (exon 19 mutations characterized by in-frame deletions of amino-acids 747 account for 45% of mutations, exon 21 mutations resulting in L858R substitutions account for 40-45% of mutations, and the remaining 10% of mutations involve exon 18 and 20); Sordella et al., Science 305:1163 (2004); and Mulloy et al., Cancer Res. 67:2325 (2007).
Unfortunately, additional mutations in the EGFR gene, e.g., the T790M mutation, produces mutant EGFR proteins to which drugs like erlotinib and gefitinib bind less well. Those mutations are associated with resistance to the drugs and to relapse in cancer patients bearing such mutation.
New diagnostic methods and therapies are needed for the treatment of EGFR-driven cancers in which mutations confer resistance to front line tyrosine kinase inhibitor (“TKI”) therapies. In particular, new therapies for inhibiting cells expressing such gefitinib-resistant or erlotinib-resistant EGFR genes could be of profound benefit.